Some considerations about the simulation of breach channel erosion on landslide dams

Cencetti, Corrado; Fredduzzi, Andrea; Marchesini, Ivan; Naccini, Mara; Tacconi, Paolo

doi:10.1007/s10596-005-9019-x

Cited by 21 publications

(9 citation statements)

References 16 publications

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“…For Scenario 4, we have selected the most unfavourable geotechnical properties from the range. A detailed explanation of the physical meaning of the parameters and the model theory can be found in Fread (1991) and Cencetti et al (2006).…”

Section: The Breach Model and Data Requirementsmentioning

confidence: 99%

Simulating dam-breach flood scenarios of the Tangjiashan landslide dam induced by the Wenchuan Earthquake

Fan

Tang

Westen

et al. 2012

Nat. Hazards Earth Syst. Sci.

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Floods from failures of landslide dams can pose a hazard to people and property downstream, which have to be rapidly assessed and mitigated in order to reduce the potential risk. The Tangjiashan landslide dam induced by the Mw = 7.9 2008 Wenchuan earthquake had impounded the largest lake in the earthquake affected area with an estimated volume of 3 × 108 m3, and the potential catastrophic dam breach posed a serious threat to more than 2.5 million people in downstream towns and Mianyang city, located 85 km downstream. Chinese authorities had to evacuate parts of the city until the Tangjiashan landslide dam was artificially breached by a spillway, and the lake was drained. We propose an integrated approach to simulate the dam-breach floods for a number of possible scenarios, to evaluate the severity of the threat to Mianyang city. Firstly, the physically-based BREACH model was applied to predict the flood hydrographs at the dam location, which were calibrated with observational data of the flood resulting from the artificial breaching. The output hydrographs from this model were inputted into the 1-D–2-D SOBEK hydrodynamic model to simulate the spatial variations in flood parameters. The simulated flood hydrograph, peak discharge and peak arrival time at the downstream towns fit the observations. Thus this approach is capable of providing reliable predictions for the decision makers to determine the mitigation plans. The sensitivity analysis of the BREACH model input parameters reveals that the average grain size, the unit weight and porosity of the dam materials are the most sensitive parameters. The variability of the dam material properties causes a large uncertainty in the estimation of the peak flood discharge and peak arrival time, but has little influence on the flood inundation area and flood depth downstream. The effect of cascading breaches of smaller dams downstream of the Tangjiashan dam was insignificant, due to their rather small volumes, which were only 2% of the volume of the Tangjiashan lake. The construction of the spillway was proven to have played a crucial role in reducing the dam-breach flood, because all the other natural breach scenarios would have caused the flooding of the downstream towns and parts of Mianyang city. However, in retrospect improvements on the spillway design and the evacuation planning would have been possible. The dam-break flood risk will be better controlled by reducing the spillway channel gradient and the porosity of the coating of the channel bottom. The experience and lessons we learned from the Tangjiashan case will contribute to improving the hazard mitigation and risk management planning of similar events in future

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Section: The Breach Model and Data Requirementsmentioning

confidence: 99%

Simulating dam-breach flood scenarios of the Tangjiashan landslide dam induced by the Wenchuan Earthquake

Fan

Tang

Westen

et al. 2012

Nat. Hazards Earth Syst. Sci.

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show abstract

“…Cencetti et al (2006) pointed out that the flow could be considered as uniform flow along a landslide dam with a large channel length but a small slope. The crest of a landslide dam is often wider than that of an embankment dam, thus the flow at the crest can be assumed to be laminar or subcritical.…”

Section: Calculation Of Outflow Hydrographmentioning

confidence: 99%

Simulation of the erosion process of landslide dams due to overtopping considering variations in soil erodibility along depth

Chang

Zhang

2010

Nat. Hazards Earth Syst. Sci.

174

103

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Abstract.A landslide dam typically comprises freshly deposited heterogeneous, unconsolidated or poorly consolidated earth materials and is vulnerable to overtopping breaching. A physically-based breach model is presented to simulate the breaching process of such landslide dams. The new model can predict the breach evolution, the erosion rate, and the outflow hydrograph. A spreadsheet is developed to numerically implement the model. The erosion processes of Tangjiashan Landslide Dam and Xiaogangjian Landslide Dam induced by the 2008 Wenchuan earthquake are analyzed using the new model. The erodibility of the two landslide dams varies significantly along depth. The predicted key breaching parameters (i.e., final breach size, failure time, and peak outflow rate) considering the variations in the soil erodibility along depth agree well with the observed values. Further sensitivity analysis indicates that the soil erodibility affects the breaching process of a landslide dam significantly. Higher soil erodibility will lead to a larger breach, a shorter failure time and a larger peak outflow rate. The erosion rate of the breach channel in the depth direction decreases with increasing erosion resistance of the landslide deposits. In the two case studies, the key breaching parameters cannot be properly predicted if constant soil erodibility parameters along depth are assumed.

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“…2.3 Incorporating heterogeneous composition of landslide dams Natural landslide dams are always composed of heterogeneous sediments (Cencetti et al, 2006;Chang and Zhang, 2010) with sizes widely distributed. Commonly, previous mathematical models deal with natural dam material with a fixed-size approach (i.e.…”

Section: Model Closurementioning

confidence: 99%

Coupled modelling of flood due to natural landslide dam breach

Huang¹,

Cao²,

Yue³

et al. 2012

Proceedings of the Institution of Civil Engineers - Water Manag

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A coupled two-dimensional mathematical model is presented for a flood due to natural landslide dam breach. A new numerical algorithm is developed, preserving the well-balanced property between the flux and source terms of the momentum conservation equations over a mobile bed. It allows for the wetting-drying transition to be properly resolved. Equally importantly, the spatially variable size of the sediments of natural landslide dams is taken into account in estimating bed sediment entrainment flux. The model is first tested against flume experiments and then applied to a case study of the Tangjiashan landslide dam, the largest of its kind generated by the 2008 Wenchuan earthquake in Sichuan Province, China. Compared with field observations, the widening and deepening of the breach along with the flood hydrographs are reproduced fairly well by the present model as the heterogeneity of the dam material is incorporated. In contrast, when the heterogeneous composition of the natural landslide dam is ignored using a fixed sediment size, the model fails even if the parameters related to roughness, entrainment flux and mass collapse are largely tuned. An appropriate account of the heterogeneous composition of natural dams is therefore significant.

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Some considerations about the simulation of breach channel erosion on landslide dams

Cited by 21 publications

References 16 publications

Simulating dam-breach flood scenarios of the Tangjiashan landslide dam induced by the Wenchuan Earthquake

Simulating dam-breach flood scenarios of the Tangjiashan landslide dam induced by the Wenchuan Earthquake

Simulation of the erosion process of landslide dams due to overtopping considering variations in soil erodibility along depth

Coupled modelling of flood due to natural landslide dam breach

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